Many tourists coming to Japan would expect to see Mt.Fuji, 3776 meters above sea level and the highest mountain in Japan.
Then, if you do not have a day to travel near Mt.Fuji, take an opportunity when taking Tokaido Shinkansen. Tokaido Shinkansen connects Tokyo and Osaka, via Yokohama, Nagoya and Kyoto, which is definitely most popular Shinkansen route in Japan.
About an hour departing Tokyo station, you may have a look of Mt.Fuji on the right side of the train. Therefore if you make a seat reservation, choose E seat for ordinary car(2nd class) or D seat for Green car(1st class).
Even it is not sunny, you may see it between clouds!